d5996b2ff0
Rabin Vincent reports:
| On SMP, this BUG() in save_stack_trace_tsk() can be easily triggered
| from user space by reading /proc/$PID/stack, where $PID is any pid but
| the current process:
|
| if (tsk != current) {
| #ifdef CONFIG_SMP
| /*
| * What guarantees do we have here that 'tsk'
| * is not running on another CPU?
| */
| BUG();
| #else
Fix this by replacing the BUG() with an entry to terminate the stack
trace, returning an empty trace - I'd rather not expose the dwarf
unwinder to a volatile stack of a running thread.
Reported-by: Rabin Vincent <rabin@rab.in>
Tested-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
132 lines
3.3 KiB
C
132 lines
3.3 KiB
C
#include <linux/module.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/stacktrace.h>
|
|
|
|
#include <asm/stacktrace.h>
|
|
|
|
#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
|
|
/*
|
|
* Unwind the current stack frame and store the new register values in the
|
|
* structure passed as argument. Unwinding is equivalent to a function return,
|
|
* hence the new PC value rather than LR should be used for backtrace.
|
|
*
|
|
* With framepointer enabled, a simple function prologue looks like this:
|
|
* mov ip, sp
|
|
* stmdb sp!, {fp, ip, lr, pc}
|
|
* sub fp, ip, #4
|
|
*
|
|
* A simple function epilogue looks like this:
|
|
* ldm sp, {fp, sp, pc}
|
|
*
|
|
* Note that with framepointer enabled, even the leaf functions have the same
|
|
* prologue and epilogue, therefore we can ignore the LR value in this case.
|
|
*/
|
|
int notrace unwind_frame(struct stackframe *frame)
|
|
{
|
|
unsigned long high, low;
|
|
unsigned long fp = frame->fp;
|
|
|
|
/* only go to a higher address on the stack */
|
|
low = frame->sp;
|
|
high = ALIGN(low, THREAD_SIZE);
|
|
|
|
/* check current frame pointer is within bounds */
|
|
if (fp < (low + 12) || fp + 4 >= high)
|
|
return -EINVAL;
|
|
|
|
/* restore the registers from the stack frame */
|
|
frame->fp = *(unsigned long *)(fp - 12);
|
|
frame->sp = *(unsigned long *)(fp - 8);
|
|
frame->pc = *(unsigned long *)(fp - 4);
|
|
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
void notrace walk_stackframe(struct stackframe *frame,
|
|
int (*fn)(struct stackframe *, void *), void *data)
|
|
{
|
|
while (1) {
|
|
int ret;
|
|
|
|
if (fn(frame, data))
|
|
break;
|
|
ret = unwind_frame(frame);
|
|
if (ret < 0)
|
|
break;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(walk_stackframe);
|
|
|
|
#ifdef CONFIG_STACKTRACE
|
|
struct stack_trace_data {
|
|
struct stack_trace *trace;
|
|
unsigned int no_sched_functions;
|
|
unsigned int skip;
|
|
};
|
|
|
|
static int save_trace(struct stackframe *frame, void *d)
|
|
{
|
|
struct stack_trace_data *data = d;
|
|
struct stack_trace *trace = data->trace;
|
|
unsigned long addr = frame->pc;
|
|
|
|
if (data->no_sched_functions && in_sched_functions(addr))
|
|
return 0;
|
|
if (data->skip) {
|
|
data->skip--;
|
|
return 0;
|
|
}
|
|
|
|
trace->entries[trace->nr_entries++] = addr;
|
|
|
|
return trace->nr_entries >= trace->max_entries;
|
|
}
|
|
|
|
void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
|
|
{
|
|
struct stack_trace_data data;
|
|
struct stackframe frame;
|
|
|
|
data.trace = trace;
|
|
data.skip = trace->skip;
|
|
|
|
if (tsk != current) {
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* What guarantees do we have here that 'tsk' is not
|
|
* running on another CPU? For now, ignore it as we
|
|
* can't guarantee we won't explode.
|
|
*/
|
|
if (trace->nr_entries < trace->max_entries)
|
|
trace->entries[trace->nr_entries++] = ULONG_MAX;
|
|
return;
|
|
#else
|
|
data.no_sched_functions = 1;
|
|
frame.fp = thread_saved_fp(tsk);
|
|
frame.sp = thread_saved_sp(tsk);
|
|
frame.lr = 0; /* recovered from the stack */
|
|
frame.pc = thread_saved_pc(tsk);
|
|
#endif
|
|
} else {
|
|
register unsigned long current_sp asm ("sp");
|
|
|
|
data.no_sched_functions = 0;
|
|
frame.fp = (unsigned long)__builtin_frame_address(0);
|
|
frame.sp = current_sp;
|
|
frame.lr = (unsigned long)__builtin_return_address(0);
|
|
frame.pc = (unsigned long)save_stack_trace_tsk;
|
|
}
|
|
|
|
walk_stackframe(&frame, save_trace, &data);
|
|
if (trace->nr_entries < trace->max_entries)
|
|
trace->entries[trace->nr_entries++] = ULONG_MAX;
|
|
}
|
|
|
|
void save_stack_trace(struct stack_trace *trace)
|
|
{
|
|
save_stack_trace_tsk(current, trace);
|
|
}
|
|
EXPORT_SYMBOL_GPL(save_stack_trace);
|
|
#endif
|